Gas detector



J n- 1949- N: E. |NDsTR0M 2,

GAS DETECTOR Filed July 28, 1944 iatented Jan. 11 1949 UNITED STATESPATENT OFFICE Application July 28, 1944, Serial No. 547,089 In SwedenJune 18, 1943 Claims.

This invention relates to an apparatus for determining the presence ofcarbon monoxide and other combustible gases or Vapors in the atmospherebeing tested. One object of my invention is to provide an apparatus ofthis kind which is a very sensitive gas detector but which neverthelessis reliable in operation and insensitive to shocks and vibrations sothat it may be used with advantage on motor vehicles and airplanes.Other objects and advantages will be more fully described hereinafter.

In its broadest aspect the gas detector according to the presentinvention comprises an expansible vessel containing a volatile mediumand a reaction chamber containing a material capable of reactingcatalytically with the gas to be detected with simultaneous liberationof heat, the expansible vessel being arranged so as to be heated andexpanded by the heat developed due to said reaction and the movement ofsaid vessel being adapted to be transmitted to a pointer or otherindicating or alarm device.

A preferred embodiment of my invention is illustrated in theaccompanying drawings, wherein:

Figs. 1 and 2 are elevations of the apparatus at right angles to eachother; while Fig. 3 is a plan view.

In the drawings l designates a base plate upon which two closedcorrugated metallic cylinders, or bellows, 2 and 3 are mounted. Eachcylindrical bellows surrounds a chamber 4 and 5, respectively. Thechamber 4 has an inlet 6 for the air or the like to be tested, and thechamber 5 has an outlet 1. The chambers 4 and 5 are interconnected bymeans of a U-shaped conduit 8. Each chamber contains a partition 9 andI0, respectively, these partitions being arranged so that the air iscompelled to flow along an extended path from the inlet to the outlet. Aholder II is attached to the top of the corrugated cylinder 2, thisholder being shaped as a fork (Fig. 3) with one leg 12 of greater lengththan the other and bent aside. At the end of the leg 12 a two-armedlever I3 is rotatably mounted, one arm of which is linked to one end ofan arm l4 whose other end is pivotally connected to the fork ll, whereasthe other arm of the lever I3 is connected by means of a link to abridge member I5 pivoting on two points it and I! carried by a bracket25 which is attached to the bellows 2. The bridge member I5 is connectedby means of an arm I8 and a wire, or a chain, with a pulley l9 mountedon a shaft 20 which carries a pointer 2|, the shaft being also actuatedby a restoring spring 22. The

details i5 to 22 are previously known from aneroid barometerconstructions and therefore need not be described more closely. The armI4 is provided with a threaded hole for a screw 23 which is adjustableand adapted to coact with a stud 24 mounted on the top of thecylindrical bellows 3.

The space between the chambers 4 and 5, respectively, and thecorresponding cylindrical bellows is substantially filled with a liquidof low boiling point, such as for instance ethyl chloride, ethyl amineor ethyl ether. The chamber 5 is filled with a reaction mass which whenthe gas to be detected is carbon monoxide may be constituted by amaterial known on the market under the trade-mark name Hopcalite andconsisting of a granular mixture of manganese dioxide, copper oxide,silver oxide and cobalt sesquioxide, this mixture being capable ofcatalytically oxidizing carbon monoxide to carbon dioxide at normaltemperatures with liberation of heat in an amount which is proportionalto the carbon monoxide content. The chamber 4 may be filled with copperborings, porcelain pieces or the like inert material.

The operation of the apparatus is as follows. When a carbon monoxidecontaining gas, for instance air, which has been deprived of itsmoisture is blown or drawn through the chambers 4 and 5 by means of apump the carbon monoxide is catalytically oxidized in the chamber 5 withsimultaneous liberation of heat. This causes the liquid in thesurrounding expansible vessel 3 to be heated so. that the pressuretherein is increased and the vessel 3 alters its length. The stroke ofthe vessel 3 is transmitted to the arm M by means of the stud 24 and thescrew 23 and as a result thereof the lever I3 is rotated causing adeflection of the pointer 21. A dial (not shown) with which the pointercoacts may be calibrated so as to show the carbon monoxide contentdirectly in per cent or fractions hereof.

Atmospheric temperature variations will not cause the pointer to bedeflected since the details I l to M constitute a differential devicewhich will transmit only a relative movement of one cylindrical bellowswith respect to the other, whereas simultaneous and identical movementsof the two cylinders 2 and 3 are without influence upon the pointer. Inthe same manner compensation is obtained also for variations in thebarometric pressure.

The details may of course be varied in many Ways without departing fromthe spirit of the invention.

When it is desired to detect carbon monoxide using Hopcalite as acatalyst the air must be carefully dried before being introduced intothe reaction chamber 5. This drying may be effected by first passing theair through concentrated sulphuric acid or over a layer of silica-gel orother highly moisture-absorbing material. Then the air is passed over alayer of pumice, lead acetate and glycerine and finally it is passedover potassium hydroxide. Drying devices of this kind are known per. se-and.do *not% form any part of the present invention.

What I claim is:

1. In a gas detecting and measuring apparatus;

a reaction chamber provided with a gas inlet an'd'i a gas outlet saidchamber being adapted to conexothermical reaction of the gas to bedetected, a second chamber connected in series with the reaction chamberand adapted to contain an inert substance, a hermetically sealed bellowsen- 5 closing said reaction chamber, and provided with expansible outerwalls, the unoccupied space Within said vessel being filled with anexpansible medium, a second sealed bellows enclosing the second chamberand providedlwith expansible outerwalls' containing the inert substance,the

space therebetween being adapted to contain an expansible medium wherebyeach of the bellows will: be. expanded in accordance with the heatdelivered by its corresponding chamber, means tain a substance capableof bringingabout' arrfor establishing relative motion on one of saidexothermical reaction of the gassto be--. detected,

a hermetically sealed vessel enclosing said"reac--- tion chamber, andprovided with expansible outer walls, the unoccupied space within saidvessel being filled with an expansible medium, an indicating= means,and' a mechanicalmotion transmittingmeans between said' expansion vesselandi said indicating means for transmitting motionlof the vessel tothe=indi cating means 2. Iii-a gas d'etectir'igl and measuring apparatusa reaction chamber 'provided with' a gas' inlet and a gasoutlet said"chamber b'eingad'apted we contair'r a-- substancecapable of bringingaboutan.-

exothermical reaction of the gas to bedetected; a hermeticallysealedwessel' enclosing said reactionphaniber: and provided-withexpansibleouter vessel to 'tlieindicating means, and means-where'-" byonly such motion transmitted" which is"- vesselsi-with respect to theother, an indicating meansg-and mechanical means for transmitting suchrelative motion to said indicating means.

5: In a gas detecting and measuring apparatus,

en a hermetically sealed vessel provided with expansib'le outer walls; aheat1tran5mission'i chamber' arrangedwithin: said hermetically sealedvessel and provided iwith gasinlet and gas outlet' channels forming acontinuous gas conduit with said heat" transmission chamber,- theunoccupied space between said vessel and said lieattrans mission 1chamber being 'filledi with an expansible medium; said" chamber beirigadapted I to contain a substance capableof bringing' about anexoindicating means, and a mechanical motiontransmitting'meansbetweemsaid i vessel 'and' said indicating" means; f or"transmitting motion -of "the vesselto theindicatingme'ansz 3.1 NILZSERIKLINDSTR'MS REFERENCES CITED The fbllbwingrefrences are offrecordinthe Yl l I L I caused by heat developed at the exotherrmcal w fileofythisppatent:

reaction;

3*. A gas. detecting and measuring? apparatusaccording toclaim'2,wher'einsaidlast mentionedi means: comprises a reference" expansionvessel" similartothat expanded: b'ifth'e heat" developed in the reactionchamber arid'adapted tobemaintained'at' the initial temperature ofthe'gasto be 4'. In a gas detectiiig',antllmeasuririg a paratus, a reactionchamber provided with a gas inlet and A a .gasoutletsaidlchamber beingadapted'tb con-- tain a substance. capable. offbringing about. an

UNITED STAT-E83 PATENTS I Number Name. Date 9703232. Hiiiman Sept.20111910v 1100?,1'78 Billings Oct. 311.1911. 1,223,953 Frisak .Apr. 24,19.17 415,710" Richter" May 9,1922 2,340,008 Matuszalc" Jan. 1944'FGREIGN PATENTS-v N umber country Date;

1601930" Great"Britain" Mar; 30, 1921 171,739. Great-Britain" Nov. 21;1921 491354" GreaVBritain Aug. 26, 1938.

